Formation of bi-aryls via a domino palladium catalysis

Article abstract of DOI:10.1016/j.tetlet.2013.12.030

Synthesis of bi-aryls via a domino Pd-catalyzed reaction of 1-(2-bromophenyl)-2-methylpropan-1-ones/(2-bromophenyl)(cyclohexyl)methanones is presented. The mechanism of the reaction is believed to proceed through a five membered palladacycle that combines with a second molecule of halo-arene to yield the bi-aryls. This method is quite successful to deliver highly sterically crowded bi-aryls with dense functionalities on the aromatic rings.

Full text of DOI:10.1016/j.tetlet.2013.12.030

Tetrahedron Letters 55 (2014) 861–864
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Tetrahedron Letters
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Formation of bi-aryls via a domino palladium catalysis
⇑
J. Krishna, A. Gopi Krishna Reddy, G. Satyanarayana
Department of Chemistry, Indian Institute of Technology (IIT) Hyderabad, Ordnance Factory Estate Campus, Yeddumailaram 502 205, Medak District, Andhra Pradesh, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of bi-aryls via a domino Pd-catalyzed reaction of 1-(2-bromophenyl)-2-methylpropan-1-ones/
(2-bromophenyl)(cyclohexyl)methanones is presented. The mechanism of the reaction is believed to pro-
ceed through a five membered palladacycle that combines with a second molecule of halo-arene to yield
the bi-aryls. This method is quite successful to deliver highly sterically crowded bi-aryls with dense func-
tionalities on the aromatic rings.
Received 18 October 2013
Revised 3 December 2013
Accepted 9 December 2013
Available online 12 December 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
[Pd]-catalysis
Bi-aryls
Domino
1-(2-Bromophenyl)-2-methylpropan-1-
ones
(2-Bromophenyl)(cyclohexyl)methanones
The development of sustainable synthetic methods is a signifi-
cant task in synthetic organic chemistry. In this regard, transi-
tion-metal catalysis is identified as a potent tool for constructing
C–C bonds most efficiently. In this context, palladium is recognized
as being among the most used metals suitable for a wide variety of
reactions, namely, coupling reactions such as Heck,1 Stille,2
Suzuki,3 Sonogashira,4 and Buchwald–Hartwig.5 In particular, C–
H activation reactions through organo-palladium intermediate
species have also become popular in the field of organic
synthesis.6,7
The bi-aryl is an important structural core present in some
biologically active natural products. For example, (+)-isoschizan-
drin,9 which is a lignin from Schizandra chinesis, has been used in
Chinese traditional medicines as an antitussive. Another natu-
rally occurring compound, steganone,10 was found to inhibit
tubulin polymerization both in vitro and in vivo. The derivatives
of valoneaic acid11 like ellagitannins, which are widely
distributed in many kinds of higher plants, possess interesting
biological activities like antioxidant and anti tumor properties
(Fig. 1).
In continuation of our ongoing research interest on transition-
metal catalysis,8 particularly on domino one-pot8f–h and sequential
domino one-pot8d,e processes, very recently, we have reported a
novel domino Pd-catalysis for the synthesis of novel 7-methyl-
5H-dibenzo[a,c][7]annulen-5-ones,8g a carbon core structure of
colchicinoid natural products.
Herein, we present an interesting domino palladium-catalyzed
reaction for the synthesis of bi-aryls. In this Letter, we present an
interesting observation that the alkyl group of 1-(2-bromophe-
nyl)-2-methylpropan-1-ones/(2-bromophenyl)(cyclohexyl)metha-
nones 3a–h/6a–h plays an important role, wherein the isopropyl/
cyclohexyl ketone moiety in the presence of a Pd-catalyst enters
into a different mechanistic path and diverts the reaction after
bi-aryl coupling unlike the previous report on 1-(2-bromphe-
nyl)ethanones (Scheme 1).8g
The 1-(2-bromophenyl)-2-methylpropan-1-one precursors 3a–
h required for this study have been accessed from the corre-
sponding ortho-bromobenzaldehydes 1a–h using isopropyl Grignard
addition and oxidation of the resulted secondary alcohols 2a–h
(for details, see: Supporting information). Having obtained the
requisite 1-(2-bromophenyl)-2-methylpropan-1-ones 3a–h, the
Pd-catalysis for bi-aryl formation was explored. However, the
reaction was unsuccessful under the optimized conditions that
were established in the case of 1-(2-bromophenyl)ethanones.8g
Surprisingly, with a slight modification of the reaction conditions
(i.e., with base K2CO3 and solvent toluene), the reaction pro-
gressed well in a very controlled fashion and furnished only
the bi-aryl product 4a in excellent yield (Table 1). The selective
formation of 4a is justified on the basis that the mild base K2CO3
would not be strong enough to deprotonate the
a-hydrogen of
isopropyl ketone 3a, therefore, the assumed simple sp3 C–H acti-
vation would be triggered by the initially formed aryl Pd(II) spe-
cies, for the formation of five-membered palladacycle. This cyclic
⇑
Corresponding author. Fax: +91 (40) 2301 6032.
E-mail address: gvsatya@iith.ac.in (G. Satyanarayana).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.12.030

862
J. Krishna et al. / Tetrahedron Letters 55 (2014) 861–864
O
R2
O
R3
Pd(OAc)2
R2
R1
R3
xantphos
R1
K3PO4, DMF
Br
150 °C
R2
R1
R3 = Me
R3 = Me
Previous Work
Me
O
R3
R2
Pd(OAc)2
xantphos
Pd(OAc)2
R3
O
R3
R2
R4
R1
xantphos
O
R1
R2
R3
R2
R3
K2CO3, toluene
K2CO3, toluene
R2
Br
R1
°
°
C
100
C
100
R1
O
R1
O
R4
R4
R4 = cyclohexyl
i
This Work
R4 = Propyl
Scheme 1. Illustration of the influence of an alkyl group on the out-come of Pd-catalysis.
OMe
OMe
Table 1
MeO
Domino Pd-catalyzed bi-aryl couplinga,b
Me
OH
Me
Me
MeO
MeO
OH
HO
O
R3
R2
Pd(OAc)2 (4 mol%)
R3
R2
Me
Me
O
xantphos (4mol%)
R1
R2
R3
K2CO3 (4 equiv)
toluene (2 mL)
100 °C, 16 h
HO
HO
COOH
COOH
MeO
R1
Br
O
R1
3a-3h
(+)-isoschizandrin
R4
4a-4h
HO
HO
HO
O
O
Me
Me
Me
COOH
O
O
BnO
MeO
H
O
O
O
OH
O
MeO
MeO
Valoneaic acid
O
O
O
H
OBn
OMe
O
Me
4a
Me
(97%)
Me
4b
Me
(85%)
Me
Me
OMe
(-)-steganone
4c
(91%)
Me
Me
Me
Figure 1. Naturally occurring bi-aryl compounds.
BnO
MeO
MeO
O
O
O
O
OMe
OBn
OMe
O
O
O
BnO
O
O
O
OBn
Pd(II) species would in turn couple with the second molecule of
3a to establish the bi-aryl bond and finally would undergo fast
reductive syn-b-elimination (due to the availability of b-hdro-
gens) than the intramolecular aldol reaction (for details, see;
Scheme 2). In the case of 2-bromoacetophenones possessing
comparatively more acidic hydrogens than that of the isopropyl
ketone 3a, relatively strong base K3PO4 was found to be success-
ful. This base is reasonably strong enough to pick-up easily the
Me
4d (84%)
Me
Me
4e (95%)
Me
Me
4f (95%)
Me
Me
Me
MeO
MeO
MeO
MeO
O
O
OMe
OMe
OMe
OMe
MeO
O
O
a-hydrogen(s) as proton(s), facilitate the formation of five mem-
OMe
bered palladacycle followed by bi-aryl coupling and undergo
exclusively intramolecular aldol condensation (due to non-avail-
ability of b-hydrogens) to furnish the 7-methyl-5H-
dibenzo[a,c][7]annulen-5-ones.8g After the accomplishment of
4a, to check the scope and limitations of the present method,
these optimized conditions were applied to the other systems
of 1-(2-bromophenyl)-2-methylpropan-1-ones 3b–h. Agreeably,
it was observed that the optimized conditions are amenable to
the other 1-(2-bromophenyl)-2-methylpropan-1-ones 3b–h and
furnished the bi-aryl products 4b–h in very good to excellent
yields (Table 1). However, in case of 4h, the reaction was found
to be slower and took a longer time when compared to other
systems, therefore, furnished the product 4h in moderate yield
(Table 1). This can be justified because of steric hindrance of
Me
Me
Me
4h
(54%)
Me
c
4g
(85%)
a
Reaction conditions: 4a–h (100 mg, 0.27–0.44 mmol), 0.14–0.22 M in toluene.
Yields in the parentheses are isolated yields of chromatographically pure
b
products.
c
Isolated yield of chromatographically pure product based on the starting
material recovery.
the di-ortho-substituents on either aromatic rings of the bi-aryl
product 4h.
In addition to the spectroscopic structural elucidation of the bi-
aryls 4, the skeletal structure of 4a has been further unambigu-

J. Krishna et al. / Tetrahedron Letters 55 (2014) 861–864
863
Me
O
O
Me
Ln-2
HBr
Me
Me
Me
Pd(0)Ln
O
Me
L
Pd(II)
Br
3a
L
path b
Pd(II)Br
2
2
A
D
path a
HBr
O
O
Me
Me
Me
Me
Ln-2
L
Pd(II)
2
Br
O
B
3a
Me
Me
Br
3a
Me
Me
Me
O
Me
O
Me
Pd(II)Br
L
OPd(II)Br
2
L
2
reductive-sy n-
β-elimination
O
O
O
Me
Me
Me
4a
Me
C
E
Me
Me
Scheme 2. Plausible catalytic cycle for the formation of 4.
tion of Pd(0)-catalyst (i.e., via path a) leads to aryl-palladium(II)
species A,13 which on intramolecular activation of sp3 C–H bond
[in this present case, the mild base K2CO3 would not be strong en-
ough to deprotonate
a-hydrogen of isopropyl ketone, therefore,
simple sp3 C–H activation would be triggered by Pd(II) species of
intermediate A is assumed] of the ketone and concomitant elimi-
nation of HBr, might lead to a five-membered palladacycle B.
Now the key palladacycle B combines with a second molecule of
3a via oxidative C–Br bond insertion and simultaneous bi-aryl
bond formation would yield Pd(II)13 complex C. Finally, expulsion
of a Pd-species via reductive syn-b-elimination might furnish the
bi-aryl product 4a. Alternatively, chelation of aryl Pd(II)-species
of A (i.e., via path b) would chelate with the oxygen of ketone
and generate the five membered palladacycle D. Coupling of palla-
dacycle D with a second molecule of 3a would furnish the bi-aryl
intermediate E, which upon isomerization could meet the interme-
diate C that has been formed via path a.
In summary, we have developed a domino Pd-catalysis for the
synthesis of bi-aryls via homo-coupling, a carbon core structure
present in biologically active bi-aryl natural products. The method
is efficient to deliver the bi-aryls with dense functionalization on
the aromatic moieties.
Figure 2. X-ray crystal structure of 4a. Thermal ellipsoids are drawn at 50%
probability level.
ously confirmed by the single crystal X-ray diffraction analysis
(Fig. 2).12
Acknowledgments
After the accomplishment of bi-aryls 4a–h, we have turned
our focus to extend the scope and limitations of the method
(the requisite precursor ketones 6a–h were prepared using
standard cyclohexyl Grignard reagent addition to the
2-bromobenzaldehydes 1 and oxidation of the resulted second-
ary alcohol 5, see: Supporting information). Therefore, Pd-cataly-
sis on (2-bromophenyl)(cyclohexyl)methanones 6a–h, was
attempted for the formation of the expected bi-aryls. Interest-
ingly, the method was also quite successful and gave 7a–h in
very good yields as shown in Table 2. Once again, the effective-
ness of substrate 7h was lowered when compared to the other
starting materials applied.
Financial support by the Council of Scientific and Industrial Re-
search [(CSIR), 02(0018)/11/EMR-II], New Delhi is gratefully
acknowledged. J.K., A.G.K.R., thank CSIR, New Delhi, for the award
of a research fellowship.
Supplementary data
Supplementary data (spectral data and copies of 1H and 13C
NMR spectra) associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.
12.030.
The plausible mechanistic paths (paths a and b) for the forma-
tion of 4a are described in Scheme 2. Initially, an oxidative inser-

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J. Krishna et al. / Tetrahedron Letters 55 (2014) 861–864
P. Eur. J. Org. Chem. 2003, 4313–4327; (d) Bellina, F.; Carpita, A.; Rossi, R.
Table 2
Domino Pd-catalyzed bi-aryl couplinga,b
Synthesis 2004, 2419–2440; (e) Suzuki, A. Chem. Commun. 2005, 4759–4763; (f)
Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem. 2005, 117, 4516–4563.
Angew. Chem., Int. Ed. 2005, 44, 4442–4489; (g) Kantchev, E. A. B.; O’Brien, C. J.;
Organ, M. G. Aldrichim. Acta 2006, 39, 97–111; (h) Saito, B.; Fu, G. C. J. Am. Chem.
Soc. 2007, 129, 9602–9603; (i) Peh, G.-R.; Kantchev, E. A. B.; Er, J.-C.; Ying, J. Y.
Chem. Eur. J. 2010, 14, 4010–4017; (j) Lu, Z.; Wilsily, A.; Fu, G. C. J. Am. Chem.
Soc. 2011, 133, 8154–8157; (k) Dreher, S. D.; Lim, S.-E.; Sandrock, D. L.;
Molander, G. A. J. Org. Chem. 2009, 74, 3626–3631.
O
Pd(OAc)2 (4 mol%)
R3
R2
xantphos (4 mol%)
R3
R2
R1
O
K2CO3 (4 equiv)
toluene (2 mL)
100 °C, 16 h
R2
R3
Br
4. (a) Casser, L. J. Organomet. Chem. 1975, 93, 253–257; (b) Dieck, H. A.; Heck, F. R.
J. Organomet. Chem. 1975, 93, 259–263; (c) Sonogashira, K.; Tohda, Y.; Hagihara,
N. Tetrahedron Lett. 1975, 31, 4467–4470; (d) Sonogashira, K. In Comp. Org.
Synth.; Trost, B. M., Fleming, I., Eds.; Pergmon: Oxford, 1991; 32, pp 521–549;
(e) Negishi, E.-I.; Anastasia, L. Chem. Rev. 2003, 103, 1979–2017; (f) Lipshutz, B.
H.; Chung, D. W.; Rich, B. Org. Lett. 2008, 10, 3793–3796; (g) Huang, H.; Liu, H.;
Jiang, H.; Chen, K. J. Org. Chem. 2008, 73, 6037–6040; (h) Severin, R.; Reimer, J.;
Doye, S. J. Org. Chem. 2010, 75, 3518–3521.
R1
R1
O
7a-7h
6a-6h
R4
BnO
MeO
5. For Buchwald–Hartwig cross coupling reactions: (a) Buchwald, S. L.; Muci, A.
Top. Curr. Chem. 2002, 219, 133–209; (b) Hartwig, J. F. Pure Appl. Chem. 1999, 71,
1417–1423; (c) Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852–860; (d) Lindley, J.
Tetrahedron 1984, 40, 1433–1456; (e) Biehl, E. J. Org. Chem. 1987, 52, 2619–
2622; (f) Kosugi, M.; Kameyama, M.; Migita, T. Chem. Lett. 1983, 927–928; (g)
Guram, A.; Buchwald, S. L. J. Am. Chem. Soc. 1994, 116, 7901–7902; (h) Louie, J.;
Hartwig, J. F. Tetrahedron Lett. 1995, 3609–3612; (i) Guram, A.; Rennels, R.;
Buchwald, S. L.; Driver, M.; Hartwig, J. F. J. Am. Chem. Soc. 1995, 117, 4708–
4709; (j) Paul, F.; Baranano, D.; Richards, S.; Hartwig, J. F. J. Am. Chem. Soc. 1996,
118, 3626–3633; (k) Driver, M.; Hartwig, J. F. J. Am. Chem. Soc. 1996, 118, 7217–
7218; (l) Driver, M.; Hartwig, J. F. J. Am. Chem. Soc. 1997, 119, 8232–8245; (m)
Wagaw, S.; Rennels, R.; Buchwald, S. L. J. Am. Chem. Soc. 1997, 119, 8451–8458;
(n) Louie, J.; Driver, M.; Hamann, B.; Hartwig, J. F. J. Org. Chem. 1997, 62, 1268–
1273; (o) Mann, G.; Hartwig, J. F. J. Am. Chem. Soc. 1997, 62, 5413–5418; (p) Old,
D. W.; Wolfe, J.; Buchwald, S. L. J. Am. Chem. Soc. 1998, 120, 9722–9723; (q)
Hamann, B.; Hartwig, J. F. J. Am. Chem. Soc. 1998, 120, 7369–7370; (r)
Kawatsura, M.; Hartwig, J. F. J. Am. Chem. Soc. 1999, 121, 1473–1478; (s)
Huang, X.; Buchwald, S. L. Org. Lett. 2001, 3, 3417–3419; (t) Kosugi, M.;
Kameyama, M.; Migita, T. Chem. Lett. 1983, 927–928; (u) Guram, A. S.;
Buchwald, S. L. J. Am. Chem. Soc. 1994, 116, 7901–7902; (v) Guram, A. S.;
Runnels, R. A.; Buchwald, S. L. Angew. Chem. 1995, 107, 1456–1459. Angew.
Chem., Int. Ed. 1995, 34, 1348–1350; (w) Khartulyari, A. S.; Maier, M. E. Eur. J.
Org. Chem. 2007, 317–324; (x) Satyanarayana, G.; Maier, M. E. Tetrahedron
2008, 64, 356–363.
O
O
O
O
O
O
OBn
OMe
7a (87%)
7b (78%)
7c (83%)
BnO
MeO
MeO
BnO
O
O
O
O
O
OMe
OBn
OBn
OMe
O
O
O
O
O
7d (85%)
7e (88%)
7f (88%)
6. For some reviews, see: (a) Kakiuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345,
1077–1101; (b) Dunina, V. V.; Gorunova, O. N. Russ. Chem. Rev. 2004, 73, 309–
350; (c) Godula, K.; Sames, D. Science 2006, 312, 67–72.
7. For some recent illustrative examples, see: (a) Ohno, H.; Yamamoto, M.; Iuchi,
M.; Tanaka, T. Angew. Chem. 2005, 117, 5233–5236. Angew. Chem., Int. Ed. 2005,
44, 5103–5106; (b) Bertrand, M. B.; Wolfe, J. P. Org. Lett. 2007, 9, 3073–3075; (c)
Rudolph, A.; Rackelmann, N.; Lautens, M. Angew. Chem. 2007, 119, 1507–1510.
Angew. Chem., Int. Ed. 2007, 46, 1485–1488.
MeO
MeO
MeO
MeO
O
O
OMe
OMe
OMe
OMe
MeO
O
O
OMe
8. (a) Reddy, A. G. K.; Krishna, J.; Satyanarayana, G. Synlett 2011, 1756–1760; (b)
Krishna, J.; Reddy, A. G. K.; Mahendar, L.; Ramulu, B. V.; Satyanarayana, G.
Synlett 2012, 375–380; (c) Suchand, B.; Krishna, J.; Ramulu, B. V.; Dibyendu, D.;
Reddy, A. G. K.; Mahendar, L.; Satyanarayana, G. Tetrahedron Lett. 2012, 53,
3861–3864; (d) Reddy, A. G. K.; Satyanarayana, G. Tetrahedron 2012, 68, 8003–
8010; (e) Reddy, A. G. K.; Krishna, J.; Satyanarayana, G. Tetrahedron Lett. 2012,
53, 5635–5640; (f) Mahendar, L.; Krishna, J.; Reddy, A. G. K.; Ramulu, B. V.;
Satyanarayana, G. Org. Lett. 2012, 14, 628–631; (g) Krishna, J.; Reddy, A. G. K.;
Satyanarayana, G. Synlett 2013, 967–972.
9. (a) Molander, G. A.; George, K. M.; Monovich, L. G. J. Org. Chem. 2003, 68, 9533–
9540; (b) Ayres, D. C.; Loike, J. D. Chemistry & Pharmocology of Natural Products:
Lignans; Chemical, Biological, and Chemical Properties; Cambridge University
Press: Cambridge, U.K., 1990; (c) Whiting, D. A. Nat. Prod. Rep. 1985, 2, 191–
211; (d) Whiting, D. A. Nat. Prod. Rep. 1987, 4, 499–525; (e) Tanaka, M.;
Mukaiyama, C.; Mitsuhashi, H.; Maruno, M.; Wakamatsu, T. J. Org. Chem. 1995,
60, 4339–4352.
10. (a) Monovich, L. G.; Huérou, Y. L.; RÖnn, M.; Molander, G. A. J. Am. Chem. Soc.
2000, 122, 52–57; (b) Kupchan, S. M.; Britton, R. W.; Zeigler, M. F.; Gilmore, C.
J.; Restivo, R. J.; Bryan, R. F. J. Am. Chem. Soc. 1973, 95, 1335–1336; (c) Tomioka,
K.; Ishiguro, T.; Mizuguchi, H.; Komeshima, N.; Koga, K.; Tsukagoshi, S.; Tsuruo,
T.; Tashiro, T.; Tanida, S.; Kishi, T. J. Med. Chem. 1991, 34, 54–57; (d) Wang, R.
W.-J.; Rebhun, L. I.; Kupchan, S. M. Cancer Res. 1977, 37, 3071–3079; (e) Zavala,
F.; Guenard, D.; Robin, J.-P.; Brown, E. J. Med. Chem. 1980, 23, 546–549; (f)
Wickramaratne, D. B. M.; Pengsuparp, T.; Mar, W.; Chai, H. B.; Chagwedera, T.
E.; Beecher, C. W. W.; Farnsworth, N. R.; Kinghorn, A. D.; Pezzuto, J. M.; Cordell,
G. A. J. Nat. Prod. 1993, 56, 2083–2090; (g) Dhal, R.; Brown, E.; Robin, J.-P.
Tetrahedron 1983, 39, 2787–2794.
11. (a) Yoshida, T.; Hatano, T.; Ito, H. J. Synth. Org. Chem. Jpn. 2004, 62, 500–507; (b)
Okuda, T.; Yoshida, T.; Hatano, T. In Progress in the Chemistry of Organic Natural
Products; Herz, W., Kirby, G. W., Moore, R. E., Steglich, W., Tamm, C., Eds.;
Springer: Wein, 1995; Vol. 66, pp 1–117; (c) Miyamoto, K.; Nomura, M.;
Murayama, T.; Furukawa, T.; Hatano, T.; Yoshida, T.; Koshiura, R.; Okuda, T.
Biol. Pharm. Bull. 1993, 16, 379–387.
c
7g
7h
(57%)
(80%)
a
Reaction conditions: 7a–h (100 mg, 0.25–0.37 mmol), 0.12–0.18 M in toluene.
Yields in the parentheses are isolated yields of chromatographically pure
b
products.
c Isolated yield of chromatographically pure product based on the starting material
recovery.
References and notes
1. (a) Beller, M.; Riermeier, T. H.; Stark, G. In Transition Metals for Organic Synthesis
In ; Beller, M., Bolm, C., Eds.; Wiley-VCH: Weinheim, 1998; Vol. 1, p 208; (b)
Bräse, S.; de Meijere, A. In Metal-Catalyzed Cross-Coupling Reactions; Diederich,
F., Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998. Chapter 3; (c) Link, J. T.;
Overman, L. E. In Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang,
P. J., Eds.; Wiley-VCH: Weinheim, 1998. Chapter 6; (d) Beletskaya, I. P.;
Cheprakov, A. V. Chem. Rev. 2000, 100, 3009–3066; (e) Poli, G.; Giambastiani,
G.; Heumann, A. Tetrahedron 2000, 56, 5959–5989; (f) Link, J. T. Org. React.
2002, 60, 157–534; (g) Lee, D.-H.; Taher, A.; Hossain, S.; Jin, M.-J. Org. Lett. 2011,
13, 5540–5543; (h) Xu, H.-J.; Zhao, Y.-Q.; Zhou, X.-F. J. Org. Chem. 2011, 76,
8036–8041; (i) Wang, Z.; Feng, X.; Fang, W.; Tu, T. Synlett 2011, 951–954; (j)
Rossy, C.; Fouquet, E.; Felpin, F.-X. Synthesis 2012, 37–41; (k) Werner, E. W.;
Sigman, M. S. J. Am. Chem. Soc. 2011, 133, 9692–9695.
2. (a) Farina, V.; Krishnamurthy, V.; Scott, W. J. Org. React. 1997, 50, 1–652; (b)
Duncton, M. A. J.; Pattenden, G. J. Chem. Soc., Perkin Trans. 1 1999, 1235–1246;
(c) Gonthier, E.; Breinbauer, R. Mol. Diver. 2005, 9, 51–62; (d) Echavarren, A. M.
Angew. Chem. 2005, 117, 4028–4031. Angew. Chem., Int. Ed. 2005, 44, 3962–
3965; (e) Huang, H.; Jiang, H.; Chen, K.; Liu, H. J. Org. Chem. 2009, 74, 5599–
5602.
12. CCDC number for the compound 2a: CCDC 910647.
3. For some reviews, see: (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457–
2483; (b) Chemler, S. R.; Trauner, D.; Danishefsky, S. J. Angew. Chem. 2001, 113,
4676–4701. Angew. Chem., Int. Ed. 2001, 40, 4544–4568; (c) Darses, S.; Genet, J.-
13. (a) Dyker, G. Angew. Chem. 1992, 104, 1079–1081. Angew. Chem., Int. Ed. 1992,
31, 1023–1025; (b) Dyker, G. Angew. Chem. 1994, 106, 117–119. Angew. Chem.,
Int. Ed. 1992, 33, 103–105.